In general, the speaker includes different types such as low frequency speakers, middle frequency speakers and high frequency speakers according to the frequency range of the sound. The low frequency speakers can play a sound with frequency below 300 Hz, the middle frequency speakers can play a sound with frequency in a range of 300 Hz-2 KHz, and the high frequency speakers can play a sound with frequency above 2 KHz.
The earphone usually includes a speaker installed in the casing of the earphone. However, the speaker is only a single type of the low frequency speakers, middle frequency speakers and high frequency speakers. Thus, the earphone can only play a single type of the low frequency sound, middle frequency sound and high frequency sound and cannot realize the complementary between the low frequency sound, middle frequency sound and high frequency sound.
What is needed, therefore, is to provide an earphone which can overcome the shortcomings as described above.